/*
 * Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: ForEach.java,v 1.2.4.1 2005/09/01 15:23:46 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.Enumeration;
import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.GOTO;
import com.sun.org.apache.bcel.internal.generic.IFGT;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeSetType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ReferenceType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ResultTreeType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 */
final class ForEach extends Instruction {

  private Expression _select;
  private Type _type;

  public void display(int indent) {
    indent(indent);
    Util.println("ForEach");
    indent(indent + IndentIncrement);
    Util.println("select " + _select.toString());
    displayContents(indent + IndentIncrement);
  }

  public void parseContents(Parser parser) {
    _select = parser.parseExpression(this, "select", null);

    parseChildren(parser);

    // make sure required attribute(s) have been set
    if (_select.isDummy()) {
      reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "select");
    }
  }

  public Type typeCheck(SymbolTable stable) throws TypeCheckError {
    _type = _select.typeCheck(stable);

    if (_type instanceof ReferenceType || _type instanceof NodeType) {
      _select = new CastExpr(_select, Type.NodeSet);
      typeCheckContents(stable);
      return Type.Void;
    }
    if (_type instanceof NodeSetType || _type instanceof ResultTreeType) {
      typeCheckContents(stable);
      return Type.Void;
    }
    throw new TypeCheckError(this);
  }

  public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
    final ConstantPoolGen cpg = classGen.getConstantPool();
    final InstructionList il = methodGen.getInstructionList();

    // Save current node and current iterator on the stack
    il.append(methodGen.loadCurrentNode());
    il.append(methodGen.loadIterator());

    // Collect sort objects associated with this instruction
    final Vector sortObjects = new Vector();
    Enumeration children = elements();
    while (children.hasMoreElements()) {
      final Object child = children.nextElement();
      if (child instanceof Sort) {
        sortObjects.addElement(child);
      }
    }

    if ((_type != null) && (_type instanceof ResultTreeType)) {
      // Store existing DOM on stack - must be restored when loop is done
      il.append(methodGen.loadDOM());

      // <xsl:sort> cannot be applied to a result tree - issue warning
      if (sortObjects.size() > 0) {
        ErrorMsg msg = new ErrorMsg(ErrorMsg.RESULT_TREE_SORT_ERR, this);
        getParser().reportError(WARNING, msg);
      }

      // Put the result tree on the stack (DOM)
      _select.translate(classGen, methodGen);
      // Get an iterator for the whole DOM - excluding the root node
      _type.translateTo(classGen, methodGen, Type.NodeSet);
      // Store the result tree as the default DOM
      il.append(SWAP);
      il.append(methodGen.storeDOM());
    } else {
      // Compile node iterator
      if (sortObjects.size() > 0) {
        Sort.translateSortIterator(classGen, methodGen,
            _select, sortObjects);
      } else {
        _select.translate(classGen, methodGen);
      }

      if (_type instanceof ReferenceType == false) {
        il.append(methodGen.loadContextNode());
        il.append(methodGen.setStartNode());
      }
    }

    // Overwrite current iterator
    il.append(methodGen.storeIterator());

    // Give local variables (if any) default values before starting loop
    initializeVariables(classGen, methodGen);

    final BranchHandle nextNode = il.append(new GOTO(null));
    final InstructionHandle loop = il.append(NOP);

    translateContents(classGen, methodGen);

    nextNode.setTarget(il.append(methodGen.loadIterator()));
    il.append(methodGen.nextNode());
    il.append(DUP);
    il.append(methodGen.storeCurrentNode());
    il.append(new IFGT(loop));

    // Restore current DOM (if result tree was used instead for this loop)
    if ((_type != null) && (_type instanceof ResultTreeType)) {
      il.append(methodGen.storeDOM());
    }

    // Restore current node and current iterator from the stack
    il.append(methodGen.storeIterator());
    il.append(methodGen.storeCurrentNode());
  }

  /**
   * The code that is generated by nested for-each loops can appear to some
   * JVMs as if it is accessing un-initialized variables. We must add some
   * code that pushes the default variable value on the stack and pops it
   * into the variable slot. This is done by the Variable.initialize()
   * method. The code that we compile for this loop looks like this:
   *
   * initialize iterator
   * initialize variables <-- HERE!!!
   * goto   Iterate
   * Loop:    :
   * : (code for <xsl:for-each> contents)
   * :
   * Iterate: node = iterator.next();
   * if (node != END) goto Loop
   */
  public void initializeVariables(ClassGenerator classGen,
      MethodGenerator methodGen) {
    final int n = elementCount();
    for (int i = 0; i < n; i++) {
      final Object child = getContents().elementAt(i);
      if (child instanceof Variable) {
        Variable var = (Variable) child;
        var.initialize(classGen, methodGen);
      }
    }
  }

}
